A typical multi-layer circuit board is formed of multiple nonconductive (e.g., fiberglass) and conductive (e.g., copper) layers. The multiple conductive layers carry signals among circuit board components mounted to the circuit board and in contact with the conductive layers.
Certain conductive layers in conventional multi-layer circuit boards include grounding layers (e.g., grounding planes) to ground certain conductive systems associated with the circuit board. For example, conventional multi-layer circuit boards include system ground layers such as a logic ground layer, a frame ground layer (e.g., a ground for a frame attached to the multi-layer circuit board), and a chassis ground layer (e.g., a ground for a chassis carrying the combination of the multi-layer circuit board and frame). The circuit board integrates (e.g. connects) the grounding layers at mesh points along the circuit board to form an integrated grounding of the grounding layers of the circuit board.
Certain conventional multi-layer circuit boards utilize sheets of conductive material, formed into z-shaped clips, to couple the mesh points of the circuit board to a support mount or carrier tray coupled to the circuit board.
Conventional multi-layer circuit boards utilize printed circuit board (PCB) mounting holes as the mesh points for the system grounds. For example, conventional 12″×14″ circuit boards have nine PCB mounting holes located in proximity to the perimeter of the circuit board, each of the PCB mounting holes having a diameter of approximately 9.5 mm.
Conventional electrically conductive side portions or stand-offs couple the PCB mounting holes to an electrically conductive support mount or carrier tray. Fasteners, such as screws, secure the circuit board, support mount, and conductive stand-offs together to secure the components and to maintain electrical contact among the components. The fasteners cause the substantially non-compliant (e.g., minimally yielding under stress) stand-offs to generate a relatively large stress on the surface of the circuit board. The stress, in turn, can break or cause failure of circuit board component ball grid arrays (BGA) positioned relatively close to the PCB mounting holes. As a result, the PCB mounting holes require that BGA devices mount to the circuit board at a 0.5 inch radius from the center of each PCB mounting hole to minimize stress on the BGA.
Manufacturers of the multi-layer circuit boards typically space or arrange the PCB mounting holes on the circuit board to minimize ground loops within the circuit board. For example, in conventional multi-layer circuit board, operation of the circuit board components create a potential difference between two adjacent PCB mounting holes in the circuit board and induce a current flow between the PCB mounting holes. Such current generates electromagnetic interference (EMI) radiation that can interfere with operation of the circuit board. By using multiple PCB mounting holes coupled to the circuit board carrier tray, the manufacturer reduces the amount of current induced among the PCB mounting holes on the circuit board and thereby reduces the amount of EMI radiation generated by current flow between the PCB mounting holes.